package com.lxb;

public class ClimbStairs {
    public static void main(String[] args) {

        int n = 4;

        if(n == 0){
//            return 0;
            System.out.println(1);
        }
        if(n == 2) {
            System.out.println(2);
        }
        int temp1 = 1;
        int temp2 = 2;
        int sum = 0;
        for(int i=3;i<=n;i++){
            sum= temp1 +temp2;
            temp1 = temp2;
            temp2 = sum;
        }
        System.out.println(sum);

    }
}
